//This code has been downloaded from http://www.geekhideout.com/urlcode.shtml on April 16, 2011
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <string.h>

/* Converts a hex character to its integer value */
char from_hex(char ch) 
{
  return isdigit(ch) ? ch - '0' : tolower(ch) - 'a' + 10;
}

/* Converts an integer value to its hex character*/
char to_hex(char code) 
{
  static char hex[] = "0123456789abcdef";
  return hex[code & 15];
}

/* Returns a url-encoded version of str */
/* IMPORTANT: be sure to free() the returned string after use */
char *url_encode(char *str) 
{
  char *pstr = str, *buf = malloc(strlen(str) * 3 + 1), *pbuf = buf;
  while (*pstr) 
  {
    if (isalnum(*pstr) || *pstr == '-' || *pstr == '_' || *pstr == '.' || *pstr == '~') 
      *pbuf++ = *pstr;
    else if (*pstr == ' ') 
      *pbuf++ = '+';
    else 
	{
      *pbuf++ = '%', *pbuf++ = to_hex(*pstr >> 4), *pbuf++ = to_hex(*pstr & 15);
	}
    pstr++;
  }
  *pbuf = '\0';
  return buf;
}

/* Returns a url-decoded version of str */
/* IMPORTANT: be sure to free() the returned string after use */
char *url_decode(char *str) 
{
  char *pstr = str, *buf = malloc(strlen(str) + 1), *pbuf = buf;
  while (*pstr) 
  {
		if (*pstr == '%') 
		{
			if (pstr[1] && pstr[2]) 
			{
				*pbuf++ = from_hex(pstr[1]) << 4 | from_hex(pstr[2]);
				pstr += 2;
			}
		} 
		else if (*pstr == '+') 
		{ 
			*pbuf++ = ' ';
		}	
		else 
		{
      *pbuf++ = *pstr;
		}
	  pstr++;
	}
  *pbuf = '\0';
  return buf;
}
